Telephone exchange system



April 9, 1935. H. D. M cPHERsoN 1,997,195

' TELEPHONE EXCHANGE SYSTEM Fi1e d- Dec. 29, 1953 1,2 Sheets-Sheet 1 INVENTOR H0. MACH-IERSON ATTOBNEZ April 1935- I H. D. M cPH ERSON 1,997,195

TELEPHONE EXCHANGE SYSTEM Filed Dec. 29, 1953 12 Sheets-Sheet 2 2H5 Bins 238 Q5 lNVENTOR E H D. MACPHERSON fiefl fl AT TORNE) April 9, 1935 H. D. M PHERsoN L J TELEPHONE EXCHANGE SYSTEM Filed Dec. 29, 1933 l2 Sheets-She a 3 ArToRA/Ey April 9, 1935. H. D. M CPHERSON 1,997,195

' TELEPHONE EXCHANGE SYSTEM Filed Dec. 29, 1933 12 Sheets-Sheet 49 IN VE N TOR H. D. AMCPHERSON April 9, 1935. H. D. M PHERSON TELEPHONE EXCHANGE SYSTEM I g l I Filed Dec. 29, 1953 12 Sheets-Sheet 5 IIIHII |||||IIIHIIIHIHIIIHIIIE IIIHIII ||||||l llllll I ll INVENTOR H. D. MACPHERSON April 1935- v Q H. D. M' PHERSON 1,997,195

TELEPHONE EXGHANGESYSTEM 7 Filed Dec. 29, 1933 12 Sheets-Sheet 6 INVENTOR H. D. MACPHERSON ATTORNEY 9 April 9, 1935. H. D. M OPHERSON 1,997,195

TELEPHONE EXCHANGE SYSTEM Filed Dec. 29, 1953 12 Sheets-Sheet 7 INVENTOR H. D. MACPHERSON ATTORNEY April 1935- D; M CPHERSON 1,997,195

h TELEPHONE EXCHANGE SY $TEM Filed Dec. 29, 1933 12 Sheets-Sheet 8 INTERMEDIATE SE NDE R FIRST SELECTOR FIG. 8

THIRD SELECTOR 4 437 [25? SENDER 700 SECOND SELECTOR FIRST SELECTOR /N VE N TOR AT TORNEV 8y H. D. MACPHERSON April 9, 1935. H. D. MaPHERSON 1,997,195

TELEPHONE EXCHANGE SYSTEM Filed Dec. 29, 1933 12 Sheets-Sheet 9 INVENTOR H. D. MACPHERSON @emd ATTORNEY April 1935. H. D. MHCPHERSON 1,997,195

TELEPHONE EXCHANGE SYSTEM Filed Dec. 29, 1933 l2 Sheets-Sheet 10 INVENTOR H. 0. MACPHERSON B A77'ORNEV April 9, 1935. H. D. M PHERSON 1,997,195

TELEPHONE EXCHANGE SYSTEM Filed Dec. 29, 1933 12 Sheets-Sheet l1 /N l/E N TOR H D. MACPHERSO/V 19y ATTORNEY FIG. "ll

April 9, 1935. H. D. MacPHERSON TELEPHONE EXCHANGE SYSTEM Filed Dec. 29, 1933 12 Sheets-Sheet l2 lNVE/VM H. D. MACPHERSON AT TORNEV Patented Aprr9, 1935 v it w :1 r t E "S ATES. PATENT crews- 45 r N s1, 997,195. 1 o TELEPHOYNETEXCHANGE' sYs'r 1 v Hugh n. MacPherson, West New Brighton, N. Y., i

assignorto Bell Telephone'Laboratories, Ineor- 'giziakted', New York, N. Y.,' a corporation of New npplication December 29, 1933, SerialNo. 704,381 r v .c c

l l'C la ims. (01. its-rise This invention relatesto telephone exchange ing to three subgroups. Forthe purpose of ade.' 7 systems and more particularly to systems in quately handling the trafiic-the invention has which connections to subscribers lines are oombeen further illustrated as havingthreesendersy. pleted by swit hin apparatusunderdifil C0117 one. sender being first choice cfor serving calls 5 trol, x e originating on any trunk of threesubgroups, the, 5

In such telephone systems provisions are made second sender being first choice forserving calls for enabling a test or repair man to establish originating on any trunk of three other. sub connections from the test desk of an office to any groups and a third sender being firstachoice for r subscribers line terminating in the office for the serving calls originating on any trunk 3015 the" 1 purpose of applying tests to determine the operthree remaining subgroups. 'It will beijobviousyloa.

ative condition of the subscribers line. It is the however, thatwhere the traffic requirements-are object oft-the present invention to improve the more severe additional senders might be -'em-, apparatus for enabling the establishment of such pl y dr ea hs nd r ing fir h i to l s h n I test connections whereby they may be more efthree subgroups of trunks. It Will also be ObVl-f fectivelyand efiiciently completed; More parous that since ea find Switch may haveac- 15G ticularly it is the objectoof the invention to process to a max mum of twenty-two trun s that: vide an efiicient, register sender common to a the-three finder switches of each sendermight plurality of trunks outgoing from-the test desk have a 6 acoeSS t0 S xty-8 r nks stea'd'of-I responsive to th dialing f subs rib rs lin to fifty-four trunks as illustrated and thatthese, v 2 designation by the test man' for setting selector trunks might b divided nto more than nine switches to select the subscribers line in accordf subg o p f 51X trunks each andthatxthe com-l ance w'ith the designation dialed, V V s mon startand sequence circuitmighthave more In accordance with the present inventionthe than nine start relayS- v i test desk has access to a plurality of'outgoing, 'E hs r r l y f h rtandsequence cirte t tr nk e ch terminating in a first t t see cuit controls a start circuit for the senderiwhich' 25 lector and all having access to-a plurality of is the p f Serving t o sp ndin equivalent register senders The out oing subgroup of trunks if such senderlisat thetime'; trunks are divided into a plurality of subgroups, idle, but if the preference sender is atthe'time v each subgroup of trunks having a start circuit busy the start circuit is extendedto the-next idle" V 7 extending to a' start and sequence circuit which sender which is norma ly the fi t C e prefer 30.; is common to all of the trunks and common to ence to other subgroups of trunks; This, is ac- ;v

the senders. The common start and sequence complished by extending the start circuits from circuit is provided with as many start relays as the common startand-sequence circuitwtogdifferthere are subgroups of trunks so that on the seient points in a chain circuit extendingover coni o zure of a trunk of one of the subgroups the corre-' tacts of the make-busy relays of all of thesenderst; 35

sponding start relay will lie-operated. A chainln addition each start -r'elay of the start and" of sequence relays is also providedfor insuring sequence circuitindicates to the 'senderqwhich that should trunks 01E more thanone subgroup be is started, which one of its three trunk finder simultaneously taken for use, but one subgroup svvitchesshould be-startedto hunt for the calling 40 start relay will be operated and that one corretrunk. Thus, for example, should a trunk of the, 4,0,

sponding tothe subgroup of trunks whose start second subgroup be taken for use, the first sender v circuit appears earliest in the chain of sequence being the preference for serving trunks ofthe first relays. The common start and sequence circuit three subgroups and this sender be, atthe' time in turn controls the association. of an idle regidle, the first of the three finder switches assoister sender with the trunk taken for use. I J ciated with thefirst sender will be startedtohunt -45.

Each sender has for thisgpurpose a plurality of I for the calling trunk. Had a trunk of the fourth trunk finders, each trunk finder-havingaccess to I subgroup been taken for use, the second sender a plurality ofthe subgroups oftrunks. For the being the preference for serving trunks of the; purposes of illustration, ,the; trunks are divided; fourth to sixth subgroups, this sender being at 7 into nine subgroups, each of which -subgroupsi the time idle, the second of the three finder '50 may comprise a maximum of six trunks and thus switches associated with the second sender would each sender may have access to fifty-four trunks. be started to hunt for the calling trunk; I 7 Each sender is thereforev provided with three ro- Thesender is arranged in the well known mantary type step-by-step trunk finders, each trunk ner to record each series of impulses dialed therer finder having access to eighteen trunks belonginto andito set upon register relays the complete i561:

designation of any subscribers line and with circuits under the control of the registers for controlling the setting of a train of selector switches to complete a connection from the trunk outgo-f ing from the test switchboard to a subscribers line. In accordance with the present invention, however, provision is made for enabling the immediate release'of the sender if a call is abandoned or the sender times out if dialing. is not completed'within a predetermined interval, provided the sender has not advanced in its selection control functions to a point where it is ready to set the final selector of the train of selector switches. If, however, the sender has started to set the final selector the abandonmentof a call or a sender time-out will not cause the immediate release of the sender, but will cause the sender to advance the final selector to tell tale on the selection control then being exercised, rather than to complete the selection as registered. 'I'he'final selector upon reaching its tell tale position will then cause the sender to be re-. 7

leased.

' For a clearer understanding of the invention referencemay be had to the following detailed descriptionin connection with the accompanying drawings in which:

Figs. 1, 2 and 3 taken together. show a test trunk first selector for establishingccnnections to sub-' 'scribers lines from a test desk, Fig. 1 showing the common toa plurality of first test trunks, one of which is illustrated in Figs. 1 to 3, inc

common to a group of senders; and

Figs. 7 tol2, inclusive, show one complete sendlusive, and

er to which the start and sequencecircuit is commen and the diagrammatic representation of two other senders. a

'lo completely illustrate the invention Figs. 8, 7, 6, 1, 3, 4 and 5 should be placed in horizontal alignment in the order named with Figs. 9, 10

andZ beneath Figs. 7, 6 and 1,respectively, Fig. 11 beneath Fig. 10 and Fig. 12 beneath Fig. 11.

The first and second selector switches illustrated in Figs. 3 and 4, respectively, are of the sequence switch type disclosed, in Patent No.

1,373,447 granted April 5, 1921 to L. Polinkowsky.

The final selector switch disclosed in Fig. 5 is of the well known panel power driven type but modified for testing purposes. The finder switches shown in Figs. 7 and 8 serve to connect the sender withany one of a main group of test trunks and are of the rotary step -by-step type having no normal position. The test trunks, one of which is disclosed in Figsl to 3, inclusive, are accessible from the cord circuit of a test desk, not shown. This test desk may be similar to that disclosed in ien q-l 6 88 gra tsdJ n 21.. 1 to 1-1- Cox. a

Initiation of atest call .It will now be: assumedthat the test man desires to make. tests on the subscribers line schematically illustrated at 550 in Fig. 5 and for that purpose inserts the plug of a test'corcl of the test desk into; the jack of a first testtrunk. For establishing a connection to the ofiice in which the desired line terminatea'a main group of fiftyfour test trunks divided into nine subgroups of six trunks each is provided. It will be further assumed that the test man plugs into jack I00 of the test trunk shown in Figs. 1 to 3, inclusive, which is in the fourth subgroup of trunks. With theplug in jack I00 an obvious circuit is established for relay III which operates, closes an obvious circuit for relay I02, at its outer back contacts disconnects ground and the winding of relay I Iii-from the tip and ring conductors I94 and I05 of the trunk and at its inner left contact transfers the outgoing sleeve conductor I05 of the trunk from battery through resistance I 01 to the conductor. of the connected cord circuit over the sleeve of jack I00. Relay I02 upon operating closes the circuit of lamps, such as I 08, as signals to other test desks that the trunk is busy, prepares the circuit of relay I03 and prevents the false operation of the auxiliary signaling circuit by opening its right back contact.

The'test man having plugged into the jack of the test trunk throws the dialing key of the connected test cord circuit thereby closing a bridge at the cord circuit comprising a polarized relay and a resistance, across the tip and ring conductors of the cord circuit thus establishing a loop circuit over the tip of jack I00, conductor I04, outer right back contact of relay I 09, conductor I I0, to ground over the lower contacts of cam 20I of "sequence switch 200, which is in position I! when the test trunk is idle; and over the ring of jack I00, conductor I05, outerleftback contact of relay I09,

conductor- I I I, upper-left and lower right contacts of cam 202.,cond'uctor I I2 to battery through the winding of relay II3. Relay H3 operates, at its left contact establishing a circuit for relay II I which in turn operates,and at its right contact completesa circuit from the sleeve of jack I00, left front contact of; relay IOI, inner left 'back contact of relay I09, winding of relay II5, right contact ofrelay II3, windings of relays H5 and II! in series to ground. Relay I I5 operates and closesan obvious circuit through the left winding of relay I 40 which operates and locksover its right winding'and inner right front contact, innerright back contact 'of relay I09 to ground atjthe right'front contact of relay IOI and at its inner left front contact closes a locking circuit for relay I02 extending over the outer right front contact and'winding of relay I02; to battery. Relay I II-operates without effect at this time and-relay II6 operates to establish a circuit extending from battery, winding of start relay 203, conductor I I8, contact of relay I I6 to grou nd. Relay 20.;

operates closing a circuit extending from ground over itsj outer right front contact, conductor H0 to battery through the winding of relay I2 0, connects ground over the right contacts of earn 204, inner right contact of relay 203, right back contact of relay 205 to the start conductor 206 which is common to the six test trunks of the subgroup extending from battery in parallel through resistance 200 and the winding of relay 208, right contacts of cam 2'l0 to conductor 2I I. Relay I20 7 operates to p e'rformfunctions to be described later; v

With relay II4'"'operated a circuit is closed.

from battery, winding "of relay l2l, right back contact'of relay I22, conductor I23, upper contacts of cami2i2, conductor I24 to ground at the alternate contacts of relay I M as long as sequence switch 200 remains in position I! and'then directly to ground over the lower left contact of cam 2 I 21 after the sequence switch advances out of position l8 and until it leaves position l3." Relay i'il upon operating connects tone current from tone coil I25 over its innerfront contacts and'trunk conductors I04 and H15 to the connected test cord circuit'as a signal that'selections are in progress, but this tone will be inaudible to the test man while the dial key is operated and ordinarilywill not be heard by him at all.

When the common start conductor 206 is grounded through the operation of relay 203 a circuit is completed through thewinding of start relay 604 of the common start andsequence circuit, thence over a chain circuit extending through the lower normal contacts of start relays 605 to 609, inclusive, to battery. Each start relay of the group GM to 609, inclusive, is. connected to an individual start conductor corresponding to conductor 206 and is thus individual-' ized to a subgroup of six test trunks, start relay 60! being individualized to the first subgroup of six trunks/relay 602 to the second subgroup of six trunks and so forth. Relay S04 upon operating in response to a calling trunk in the fourth subgroup of trunks looks over its inner lower front contact directly to battery and opens at its lower normal contacts the chain circuit extending over the lower normal contacts of relays 603,682 and 1 6D! to prevent the operation of any one of these relays should a trunk in any one of the first three subgroups of trunks be thereafter placed in a call ing condition. The seizure of a trunk in any sub group to which start relays 605 to 669 are-individualized will, however, cause the operation of the'proper one of-these relays. Relay 604 also completes a circuit from battery through the winding of relay EM over the inner upper front contact and upper alternate contacts'of relay 5134 in parallel, thence over a chain circuit extending through the inner upper and outer upper back contacts in parallel of relays 603, 602 and GM to ground. At its inner upper and outer upper back contacts relay $04 opens the chain circuit extending through the upper contacts of relays [Hi5v to 809, inclusive, which supply ground to the windings of relays M5 to 519, inclusive, so that should any one of relays 604 to 609 be operated it would not be able to complete the circuitof the corre-.

sponding relay in the group M5 to BIS, inclusive.

This arangement of relays EDI to 6839, inclusive, prevents more than one of relays 6H to H9, inclusive, from operating at a time and therefore prevents more than one sender from hunting at a time.

It will be assumed that the sender disclosed in full in Figs. 7 to l2,'inclusive, is the preference sender for any calling trunk in subgroups 4, 5 and 6 and that at the time the start relay 6M operates itis idle and available to serve the callingtrunk. When, therefore, relay 6M operates as previously described, it closes a circuit from ground at its upper contact over conductor 6B9, inner leftback contact of the sender makebusy relay H10, winding of start relay ml, con-' and for furnishing holding ground for subse- Relay 'HH operates, connects O'fi'i'" quently operated relays. of the sender, andpreL-J. paresa circuit for relaylfifi'. Relay 6L4 also'co nects ground over its inner lower front contact, conductor. Slil, the middle left front contact-of relay 'lfll, conductor 1B5 to-battery throughi'the winding of relay. 853. Thus the operation-10f relay GM of the start circuithas caused the seizure of the preference sender and prepared the'proper one 896 of its three associated trunk finders 15B, 86B and 859 for operation to hunt for the calling trunk. Itis to be 'noted'that finder Bil?! has access to the 'first three subgroups of trunks comprising trunks l to l8,inclusive, that finder 8 5d has; access to the second; threesubgroups of trunks comprising trunks l9to 3G, in; elusive, and that finder lliiihas access tothelast three subgroups. of trunks. comprising trunks 31 to 54, inclusive. 1 p

All test trunks "to "which the finder fhas access, which arein a non-calling condition,iwill' be marked on the, test terminals of are 851 of finder 859 byground,-and assuming that this 4 finder is at the time standing in the position il-' lustrated, ground on the test terminal uponwhich wiper B52 is standing, middle upper contact of relay a circuit "will be established from 853, conductortfid, inner right front contact of relay 10 I, winding of relay H15 to battery. Relay will therefore operate and close a circuit for the pulse help relay 19! extending from battery,

winding of relay 1G7, conductor 108, back con-f tacts of stepping magnets 805, 855 and 155, right. front contact of relay to ground on the test relay 853 operated, it closed a circuit which may. be traced frombattery, winding of relay'109, right normal contacts of relay ll9,"ccnductor 'terminalof are 859 as previously traced' When 1 H l, to ground at the inner, lower front contact.

of relay 853. Relay Hi9 operates and extends its operating ground to the winding of relay 1:10.

cult is established for the stepping r 1agnet-8{'a5-v of finder 858, which may be traced from battery; winding of magnet 855, lower contact of relay.

853, ccnductortfifi to ground at'the 'contactso'f: relay 151?. its contacts the circuit 'of' relay T0! which re? leases in turn releasing magnet 855 to advance the wipers of finder 850 one step. If, as assumed; thenext' trunk to which this finderhas accessv is also in a non-calling condition, relay lES will remain operated again causing theoperation of relay E81 and magnet 355 to stepthe finder another step. In this'manner the finderwill' be advanced until-the test wiper 852 engages'a Magnet 855 now operates opening at test terminal of its are which is ungro'un'ded,

denoting a trunk which is in a calling condition. Thus when wiper 8-32 engages'the test terminal to which conductor Ziir ofthe c'allingtrunk is connected no circuit will be eifective to reoperate relay 'lil'l' and to hold relay 365 .operated'and re-'* lay will therefore release in turn releasing relay 1%. With relaysl'il i and 109 both released and relay Hi3 operated. a-circuit is now closed for relay H3 extending from'bat-tery, winding of relay 153, left back'contact of relay 'ifilifbackc 2 contact of relay its, outer leftwfront co'ntact ofrelay H0, back contact of relay I05 to ground atthe back contact of relay ."II2. Relay "H3 op-' erates, looks over its inner left contact, back contact of relay I09,- thence as just traced to ground atthe back contact of relay H2 and establishes a circuit from ground through the low resistance left winding of relay 'II4,- left back contact of relay'II5, outer left contact of relay H3, conductor .TIB, middle lower contact of relay 853,

wiper 851 of finder 850 and the terminal of arc:

858 upon which it is resting, conductor 2I I, inner left front contact of relay 2E3, right contacts of cam 2I0. to battery through resistance'209 and the winding of relay 208 in parallel.

Relay 208 cf the first test trunk and relay H4 a of the senderboth operate over this circuit due to the low resistance of the left winding of relay; 1I4. Relay H4 upon operating in turn causes the operation of relay I I I over an obvious circuit. Relay II! at its left contact closes an obvious operatingcircuit for relay I03 and a holding circuit for relay 853. The holding circuit of relay 853 may be traced from battery, winding and inner upper front contact of relay 853, conductor H8 to ground at the left contacts of relay ;'II"I.

Relay 103s upon operating connects ground over its inner left front contact to the sender 01fnorinal conductor I04, connects battery over its outer right front contact to conductor I000 for front contact, and at its right back contact opens the circuit of start relay 10!. 'Relay I! now releases opening the initial operating circuit of relay 853, disconnecting the winding of relay I from the test wiper 852 and establishing a circuit from ground through resistance 'IIS, both windings of relay "H2, right'back contact of relay 'IOI, conductor 854, middle upper contact of relay 853, test wiper 852 and the terminal of itsarc85I upon which it is resting, conductor 20], front contact of relay 208, winding of relay 205 to battery. Relay H2 operates in this circuit but due to the resistance of the windings of relay'IIZ relay 205 does not'operate at this time; Relay H2 upon operating opens the holding circuit of relay H3 which now releases, and short-circuits resistance H9 and itsown right winding, allowing sufficient current to flow over the previously traced circuit through the winding of relay 205 to permit its operation. Relay 205 upon operating connects direct ground over its outer left front contact to conductor 201 thusshunting the left winding of relay I I2 and causing relay I I2 to release. With relay II2 released, relay I03 operated, and relay I I 3 released a circuit is closed from battery, winding of relay 859, upper front contact of relay 853,

conductor I20 and in parallel therewith from battery through the left winding of sender makebusy' relay I00, thence over the right back con-- tact of relay ,II3, outer left front contact of relay 183, back contact of relay I09, outer left front 2 I6 from the test trunk over the terminals of arcs 860, Nil, 862 and 863 and the associated wipers 884, 865, 866 and 867 to the sender, and relay I00 upon operating extends conductor 600 over its left front contacts in parallel to conductor 620 which is the start conductor extending from the start and sequence circuit to the intermediate senderwhich is the normal preference for serving any calling trunk in the first three subgroups of trunks. Should any trunk in the fourth, fifth or sixth subgroups of trunks be in a calling condition, the operation of any one of relays 6M, 6I5

or BIG will now apply ground to conductor 600.

and thence as traced to conductor 620, or if any trunk in the first, second or third subgroups of trunks bein a calling condition the operation of any one of relays BI I, 6 I 2 or 6 I 3 will apply ground directly to conductor 620. If the intermediate sender, portions of which are schematically illustrated by the dot-dash rectangle in the lower right portion of Fig. -8, is at the time idle the start conductor 620 will be extended over the left back contacts of make-busy relay I00 of that,

sender to'the winding of start relay I0! thereby starting such sender for serving the calling trunk. The trunk finders of this sender are schematically illustrated at 750, 800' and 850. Should this sender be busy and its make-busy relay I00 be operated then conductor ,620 would be further extended over the left front contacts of relay I0 I to conductor 630 whichis the start conductor extending. from the start and sequence circuit to the last sender'which is the normal preference for serving any calling trunk in the seventh, eighth and ninth subgroups of trunks. Should any trunk in the fourth, fifth or sixth subgroups of trunks be in a calling condition the operation of any one of relays M4, M5 or 6I5 will now apply ground to conductor 600 and thence as traced over conductor 620 to conductor 630, or if any trunk in the first three subgroups be in a calling condition over the outer left back contacts of make-busy I ing the calling trunk. The trunk finders of this sender are schematically illustrated at I 800 and 850 As afurther example, it will be assumed that a trunk in one of the first three subgroups of trunks is in a calling condition and that one of relays 6H to M3 has grounded start conductor 620 and the intermediate sender whichis the normal preferencefor serving trunks of these subgroups is busy and the make-busy relay I00 thereof is operated. Conductor 620 will now be extended to conductor 630 over the left front contacts of relay I00. Ifit now be assumed that the last sender which is second choice preference to these subgroups of trunks is also busy, conductor 62!! will be further extended over conductor 530, the

choice preference to that subgroup of trunks, to

start relay 'IOI. Thus it will be apparent that al- 901 operates closes a locking circuit for itself extendingfrom battery through its lower winding and inner lower front contact, Winding of,

relay I I 01, back contact of transfer relay I I20,

conductor H08, inner right front contact of relay 1I1, conductor II 09, back contact of transfer relay I206, back contact of transfer relay I226, conductor HID, right front contact of relay 901,

left front contact of relay 903 to ground on con- 7 ductor- 104. Thus before relay 901 operates to 'suchan extent as 'to' release recording relays :9I'2 an'd 9I3, and in turn open the initial operatingcircuit 'of register relay HOI, relay I IOI has become locked;

:Transfe'r relay I I01 operates in the locking circuit: of relay IIOI'and locks itself in series with register relay II I over its upper fronticontact to ground on conductor 104, opens at its back contact the circuit of transfer relay H06which now releases and at its inner upper front con-.

tact establishes a circuit from: ground onconductor 104, back contact of relay '1 I21, winding,

of transfer relay H26 to battery" The release of transfer relay I I06 disconnects the circuits extending from the contacts of the impulse. re-

cording relays'from the operating windings .of

therelays of the thousands register I I00 and the operation of transfer relay I I20 connects these circuits to the operating windings of the relays of the hundreds register i I20. At its upper back contact relay H26 also opens the initial operating circuit of relay I I 01.

In response to the first impulse of the second digit 3, relays 990 and 90I release, reoperating relay 906, and releasing relay 901'and operating recording relay 9I3 over the previously traced circuit. Relay-1H Zoperates in the locking circuit relay'9l3 upon. the next energization ofrelay 900 and closes a circuitfrom ground over conductor 9, the middle lower contact :of trans operated; the impulsing circuit. from the back contact of lrelay 900 is extended as previously tracedto the left back contact of relay 9H, hence over the right front contact of relay 9I2 to battery. through the winding of impulse recording relay 9J6. Relay ,9I0 operates and locks in a circuit through its windingand the wind ing of relay9'H in series, front contact of relay 9I0, right back contact of relay 909, thence over conductor 9I5 to groundzon conductor-104as traced, and relay 9| I, operates in this locking circuit upon the next energization of-relay 900. Re-

lay 9I I upon operatingopens the holding circuits of relays 9I2 and 9I3 at its right back contact and'these relays now release/Relay 9I2 upon releasing opens the-previously traced circuit through the winding of registerrelay II2I which also releases. On the next release of relay 900, the impulsing circuit'from the back contact of relay 900 is extended'as previously traced to the left back-contact of relay 9I0, thence over the left front contact of relay 9 II, to battery through the winding of impulse recording relay 9. Relay 9I'1'operates and locks in a circuit through its winding and. the winding of r'e1ay'9I0 in series,'front contact of relay 9I1, right back contactof relay-909 to ground on'conductor 9 I5. Re-

next energization of relay 900. a remainsoperated for an appreciable interva n relay 906 releases in turn causing the operatic1 lay 9H! operates in this lockig h of vrelay=901 to 'open'at its inner contact the holding circuit over conductor 9I5 for the operated recording relays 9H, 9I6, 9I0 and 9H.

' Before the release of. the recording relays, however, relay 9II upon operating closed a circuit from ground at itsright front contact, conductor 9 I B, inner lower contact of relay I I26, lower winding of relay H22 of the hundreds register H20 to battery and relay 9I0 upon operating closed a circuit from ground at its right front contact, conductor 9I4, middle lowercontact of relay I I26, to battery through the lower winding of relay "II2I. Relays H2I and H22 both operate and close locking circuits for themselves in parallel from battery through their upper windings and front contacts, thence through the winding of relay H21, conductor H08, and as previously traced to conductor IIIO, thence over the right front contactof relay 901, left front contact of relay 903 to ground on conductor 104. Relay the. contacts of therecording relays and the operation of transfer relay I 209 connects the operating windings of the relays of the tens register I290 to the contacts ofthe recording relays.

Relay g m response to the first impulse of the third 7 digit 1, relays 900 and MI release, reoperating relay 906, and releasing relay 901. Relay 990 upon releasing also operates recording relay 9| 3 over the previously traced circuit. Relay 9I2 then operates as previously described upon the next energization of relay 900. In response to the next two impulses dialed, recording relays 9H, 9I6,9I0 and SH operate and-relays 9I2 and 9I3 release as previously described, relays 9I0, 9H and 9| 2 closing operating circuits over conductors 9M and 9I8 and the middle and inner lower front contacts of transfer relay I 206 for relays I20I and I202of the tens register I200. Since, however, relay 901 is not at this time operated, these register relays do not close effective locking circuits for themselves.

In response to the fourth impulse of this digit, relay 900 again releases and with relay 9I0 operated closes the impulsing circuit from its back contact, as traced to the left back contact of relay 909, left front contact of relay 9I0 to batterythrough the windingof recording relay 9I9. Relay 9I9 operates and locks in a'circuit through its, winding and the winding of relay 909 in series, front contact of relay 9 I 9, outer right back contact of relay 903 to ground over conductor 9I5. Relay 909 operates in this locking circuit upon; the next energization of relay 900. Relay 909 upon operating opens the holding circuit of relays (H I, 9I6, M0 and 9H at its right back contact whereupon these relays release, relays 9H and 9I0 in turn releasing register relays I20I and I202. At its right front contact relay 909 also V om ground over conductor 929, a i i i Contact of transfer relay 52%, lower of relay I293 of tens register I200 to bat- Since, however, relay 90! is'not at this time operated, relay i293 does not close an effective locking circuit for itself. 2 i

In response to the fifth impulse, relay 900 again releases and with relay 909 operated, closes the impulsing circuit from its back contact as traced, to the left back contact of relay 908, left front contact of relay 999 to battery through 'the'winding of impulse recording relay 92L Relay 92! operates and locks in a circuit through its winding and the winding of relay 908 series, front contact of relay 92I,- right back contact of relay 9| I to ground on conductor 915, Relay 908 operates in this locking circuit upon the next energization of relay 900 opening atits outer right back contact the locking circuit'of relays 999 and 9I9 which now release. Relay999 upon releasing in turn releases the operated register relay i203. Relay 908 also closes a circuit extending from ground onconductor' 9I5,' outer right contacts of relay 999, right back contact of relay 922, to battery through the winding of relay924. Relay 924 operates and closes 'a'locking circuit for itself extending from battery through its winding andthe winding. of relay 922 in series, front contact of relay 924 to ground onconductOr'S'IS, butrelay 922 does not operate in this locking circuit so long as relay'908 remains operated Relay 998 also closes a circuit extending from ground at its inner right 'front contact, left back contact of relay 922; conductor 923, lower contact of transfer relay I209, lower winding of relayjliltl l of the tens register I290 to battery. Relay I294-upon operating prepares a'locking circuit for itself which will be traced hereinafter.

Iii-response to the sixth impulse, relay 990 again erates inthislocki ng circuit upon the next energization of relay 900. Relay 9I2 also connects ground to conductor 9I4 thereby closing the'previously traced circuit through the lower winding of relay I20I of tens register I200 to battery. Since, however, relay 901 is'not at this timeoperated, relay I29I does not close an effective locking circuit for itself.

In response to the seventh and last impulse of this digit series, relay 990 again releases and with relays 998 and 9I2 operated, closes the impulsing circuit from its left back contact as traced to the left back contact of relay SI I, thence over the right front contact of relay V9I2 to battery 7 through the winding of relay BIB; Relay 9; 0p-

erates and 'closes a locking circuit for itself through its winding and the winding of relay 9I I in series, front contact of relay 9I6, right back contact of relay 999, to ground on conductor 9I5 and relay 9 operates in this locking circuit upon the next energization of 'relay 900. Relay 9 upon operating opens at its right back con tact, the locking circuit of relays9I2, 9 I3, 908 and MI which new release. Relay 908 upon releasing'permits relay 922 to operate Relay 9I'2 upon releasing opens the operating circuit of register relay I20I which also releases. At its right front contact, relay'9II closes the circuit previously traced over conductor 9I8 to battery through the winding of register relay I202 which operates and prepares a locking circuit for itself. Relay 998 upon releasing opens the previously traced circuit over conductor 923 for the register relay I204, but with relay 922 now operated, the circuit is reclosedfrom conductor 923 over the left front: contact of relay 922 to ground atthe inner right and back contact of relay 908' and register relay I204 reoperates. Thus at the end of the third digit series, relays I202 and I204 are the onlyrelays of the tens register I200 which remain operated. Relay 990 now remains operated for ana preciable interval whereupon relay 906 releases and relay 901 operates to open at .its innercontacts the holding circuit over conductor 9I51 for the operated recording relays 9I I, 9I6, 922 and 924. Before the release of theserelays and the consequent opening of the operating circuits of register relays I202 and I204 controlled thereby, relays I292 and I204 close locking circuits for themselves extending from battery through their upper windings and upper contacts in parallel, winding of relay I207, back contact of transfer relay I226, conductor I I I9, outer right frontcontact of relay 901, left front contact of relay 903 to ground on conductor I94. Relayv I201 operates in this locking circuit, locking itself and relays I292 and I294 over its upperfront contactconductor III2, outer. right'contact of relay "'II'I, conductor IIII, upper front contacts of relay I I21, to ground on conductor I04, opening the operating circuit of transfer relay I206 at its lower back contact, and closing a circuit from ground on' conductor I'I I2 over its inner upper front contact, the lower back contact of relay I221 to battery through the" winding of transfer relay I225.

Relay: I206 upon releasing disconnects the op-,

erating windings of the relays of the tens register I299 from the contacts of the recording relays and the operation of transfer relay I226 connects the operating windings of the relays of units register I220'to the contacts of the recording relays. v 7 V In'response to the first impulse of the fourth digit zero, relays 909and 90I release, reoperating relay 909, releasing relay 901 and operating recording relay 9I3. Relayv 9I2 then operates as previously'described upon the next energization of relay 900. In response to the next six impulses, the recording relays operate and release as previously described, so that when relay 900 reoperates at the end of the seventh'impulse, recording relays 9II, 9I9, 922 and'924 are operated and circuits are closed by relays 9II and 922 over conductors 9I8 and 923, the inner lower. and lowermost contacts of transfer'relay I226 and the lower windings of relays I222-and1224 of the units register I229 to battery. Relays I222 and I224 will therefore be operated to prepare locking circuits for themselves.

In response to the eighth impulse, relay 900' again releases and with relay 9 operated closes; the impulse circuit from its back contact, thence as traced to the left back contact of relay 908;

left back contact of relay 909, left back contact in, j

of relay 9I0, left front contact of relay 9I Ito hat-- 7 tery through the winding of relay9I'I. Relay 9 I 1' operates and locksin a circuit throughits winding and the winding of relay 9! in seriesfront contact of relay 9I'I, right back contact :of relay Relay I22I operates and prepares a locking cir- H cuit for itself.

.In response to the ninth impulse, relay 900 releases and with relay 910 operated closes-the impulsing circuit from itsback contact thence as traced to the left back contact of relay 908, left back contact of relay 999, left front contact of 1 relay 9 I to battery through the Winding of relay 9I9. Relay 9I9 operates and locks in a circuit through its winding and the winding of relay 999 in series, frontcontact of relay 9I9, outer right back contact of relay 908, to ground on conductor 9 I 5. Relay 909 operates. on the next energization of relay 999, closes the circuit over conductor 929 and the inner upper contact of transfer relay I226, to .battery through the lower winding. of relay I223 of the units register I229. and opens the locking circuit of relays 9I I, 9I5, 9I0 and 9II at its right back contact. Relays 9| I, 9I6, M0 and SI! now release in turn releasing register relays I22I and I222.

In response to the tenth and last impulse, relay 999 releases and with relay 999 operated, closes the impulsing circuit from its back contact, thence as traced over the left back contact ,of relay 998,left front. contact of relay 909, winding of relay 92I to battery. Relay 92I operates and locks in a circuit through its winding and the winding of relay 998 in series, front contact of relay 92I, right back contact of relay ill I to ground on conductor 9I5. Relay 998 operates in this locking circuit upon the next energization of relay 999 and opens at its right back contact the These re-- locking circuit of relays 999 and 9I9. lays new release, relay 999v in turn opening the operating circuit of register relay I223. With relay 922 operated, relay 908 upon operating opens the circuit previously traced over conductor 923 through the operating winding, of register relay I224, whereupon relay I224releases. Relay 998 also closes a circuit from ground at its'inner right front contact, over the inner right front contact of re1ay'922, conductor 925, upper front register relay I225 to battery, thus at the end of the fourth digit series, relay I 225 is the only relay of the units register I 220 Which is operated.

Relay 909. now remains operated for an appreciable time, whereupon relay 906 releases and relay 99! operates to open at its inner contacts the holding circuit over conductor M for the operated recording relays 908, 02I, 922 and 924. Before the release of these relays and theconsequent opening of the operating circuit of register relay I225, relay I225 closes a lockingcircuit for itself, extending from battery through-its upper winding and contact, winding of relay I221, conductor IIIO, outer right front contact of relay 901, left front-contact of relay 993 to ground on conductor I94. Relay I221 operates in this circuit, locking itself and register relay I225 over its upper front contact, conductor ,I I I2,.outer right contact of relay lII, conductor IIII, upper front, contacts of relay II 2! to ground on conductor I04, opening the operating circuit of transfer relay I229 at its lower back contact and closing a'circuit from ground on conductor I I I2 over itsinner: upper front contact, conductor III3 to battery through the winding or leg; I alay I226 upon releasing disconnects the'E': ing windings. of the relays of the units refit?! I229 from the contacts of the recording relays and relay 995 upon operating opens the circuit of relay 994 which now releases. 7

Setting the test trunk first selector for the a two thousands selection I As soon as the first digit dialed has been registered, in the case assumed by the operation and locking of relay II9I of the thousands register H00 and relay N91 has operated as previously described, a circuit is closed for relay I993 which may be traced from battery, front contact of relay mm, which operated over the back contact of counting relay- I092 when ground was applied to conductor 194.upon the seizure of the sender,

thence over the lower back contact of relay I094,

conductor I995, lower front contact of relay H01 to ground on conductor .104; Relay I093 operates and closes a circuit from ground on conductor I94, inner upper front contact of relay H93, upper back contact of relay I994, conductor I 906, winding of transfer relay III4 to battery. Relay II I4 operates and closes a circuit from; ground over its lower front contact, conductor I901 to battery through the winding of relay I 998. Relay I998 operates and with relay I993 operated closes an operating circuit for relay I909, extending from battery, winding of relay I099, upper contact of relay I998, upper contact of relay-I993,- to ground on conductor I94. A holding circuit for relay .I I I4 is now closed from battery, winding of relay III4, conductor I999, upper winding of relay I 094, conductor I0 I 9, inner lower front contact of relay I I I4, conductor I9I I, lower contact of relay I999 to ground on conductor 794,'but relay I904 being shunted so long as relay I993 remains operated does not operate at this time. V

With relay I998 operated, ground is connected to conductor I M 2 to afford locking ground for certain of the counting relays and ground is connected over the upper contact of relay I M4 to conductor I9I3 to afford locking ground for the remainder of the counting relays. A fundamental selection control circuit is now closed from battery, winding of selection control relay 39I of the first or two thousands selector of Fig. 3, conductor 302, left contacts of cam 2I9, fundamental tip conductor 2I5, wipers 866 of trunk finder 850, outer right contact of relay 859,-conductor I22, upper contact of relay I999, resistance I OH, winding of stepping relay I M 5, conductor -I9I6, back contact of counting relay I9Il, conductor I9I3, right back contact of relay H5, conductor I23, inner left contact of relay 859, wiper 891 of finder 859, fundamental ring conductor 2I6, upper left contact of cam 229 to ground at the lower right contact of cam 22 I. 7

Control relay 39I and stepping relay IOI5 both operate over this circuit, relay 39I upon operating closing a circuit extending from ground at its left contact, over conductor 303, the upper rightand lower left contacts of cam 222, conductor 223 to battery through the winding of relay 394. Relay 394 operates and locks over its inner right contact directly to ground at the left contact, of relay 39I and closes a circuit for advancing sequence switch 299 out of position I into position 2 which may be traced from battery, magnet winding of. sequence switch 209, upper contact of cam 2II, lower left contact of cam-224, conductor 225 to ground at the outer 

